1. Field of the Invention
This invention relates to reducing the peak power requirements of printers, particularly printers having work stations that are powered on an on-demand basis.
2. Description of Related Developments
Many types of reprographic equipment, such as those using electrophotographic reproduction techniques, are in use. Such equipment incorporates work stations that are maintained at predetermined operating power levels. To assure acceptable image quality, a relatively constant speed sheet transport system is used. As a consequence, the power input required by such equipment tends to be relatively constant, after start-up conditions are reached.
Recently, thermal ink jet printing has been developed as an alternative to the fused toner imaging techniques used in electrophotographic and other hard copy imaging equipment. Thermal ink jet printing is basically an on-demand system that requires almost no power at idle conditions but requires high power under high speed, high image density conditions. An advantage of ink jet printing is that image quality does not deteriorate at high throughput rates, in comparison to other methods. The power input excursions in the duty cycle of thermal ink jet printers result from the need to boil the liquid component of the ink (usually water) twice, once in jetting the ink onto the recording medium and a second time in drying the ink and fixing it on the recording medium. To maintain overall power consumption low, it is desirable to use on-demand dryers, such as microwave dryers, that also have widely varying power input requirements governed by copy speed and ink density. For an ink jet printer or marking engine operating at 30 copies per minute, printing with black ink only at a high image density, approximately 2500 watts of power are required. For a 90 copy per minute process color printer, with an high image density, approximately 15,000 watts are required. These power requirements tend to come in bursts, one as the thermal ink jet printer bars are operated and the other as the recording medium passes through the microwave dryer. This results in significant peak power excursions over the duty cycle of the printer. However, from a user acceptability standpoint, it is desirable that normal power lines, such as the 1.5 KVA receptacle terminated lines commonly found in offices and homes, be capable of meeting the power requirements of such printers. This avoids the cost of installing special power lines and allows flexibility in placement of the equipment.